The invention relates to a method for the preparation of a non-sticky (so-called non-caking) powder, whereby a concentrate of minimally 48% dry solids content is consecutively spray-dried in a tower and the dry product thus obtained is subjected, at a moisture content of at least 10%, to a crystallization, whereafter a final drying produces the end product. A problem which occurs when such methods for the preparation of a hygroscopic and/or thermoplastic product like whey powder are carried out, is the stickiness of the powder at the prevailing temperature and moisture. Starting from a solution of the indicated percentage dry solids content mentioned above, this solution is normally dried until an end moisture content not lower than 10% and preferably 12-14% is obtained, in other words: a dry solids content of maximally 90%.
In this so-called "wet-system" an after-crystallization and final drying are carried out. Thereby the final moisture content mentioned of at least 10% is necessary, so as to have sufficient moisture available to be bound as water of crystallization. In this system the earlier mentioned phenomenon of caking or building up of powder particles may happen, both in the drying tower and in the discharge channels of the dryer. This is caused by the high moisture content of the drying air. This can for instance be prevented by means of introducing extra drying air in these discharge channels.
Problems arise especially when using acid whey powder, that is to say, a powder of which a part of the lactose is converted into lactic acid. This latter powder is very hygroscopic and sticky. It has already for some time been attempted to convert acid whey into a powder, which is sufficiently loose, which flows easily, dissolves quickly, has a good flavor and can also be stored for a reasonable period without any caking occurring. Hitherto it was thought to be able to accomplish this by reducing the hygroscopic properties of the powder. The hygroscopic property can be reduced by converting the lactose into the crystallized d-hydrate form during operation as efficiently as possible. The known method did not meet the requirements mentioned hereinbefore satisfactorily.